The present invention relates generally to the field of vehicle emissions measuring systems and, more particularly, to an improved on-board exhaust particulate measuring system.
Motor vehicle emissions are the leading source of air pollution in most metropolitan areas, causing health, ecological and economical damage. As a result, considerable effort and resources are currently devoted to various emission reduction strategies, such as emission inspection programs, reformulated or alternative fuels, stricter standards for new vehicles, mass transit, improved engine control and catalyst technologies, and upgrade and repair of existing vehicles. However, in order to evaluate the impact of these reduction strategies, it is necessary to measure and collect accurate real-world emission measurements over the life of a vehicle.
Presently, the vast majority of emission tests are performed in a specialized laboratory, where the vehicle is driven on a dynamometer according to a prescribed driving cycle, such as I/M 240 or FTP for light and medium duty vehicles and CBD for heavy duty vehicles.
This approach has several significant disadvantages. First, the driving cycles do not adequately represent real-world driving conditions, which vary and are often unknown. Second, vehicles can be optimized for low emissions during the driving cycle, but do not operate optimally in actual use. Third, the testing equipment is bulky and expensive. Fourth, there are significant costs associated with testing the vehicle, such as vehicle (and/or mobile laboratory) mileage, vehicle downtime, and the test it-self, especially on heavy-duty vehicles. Fifth, individual vehicle engines have unique characteristics which effect emissions and cause variations between vehicles. Sixth, only a relatively small number of vehicles are being tested.
The first two disadvantages can be eliminated by using a capable testing system installed in the vehicle. Such systems can be classified into four categories: (1) laboratory-grade instruments permanently installed into dedicated instrumented vehicles (2) repair-grade gas analyzers used primarily by automotive technicians and providing only a rough estimate of mass emissions for repair purposes, (3) portable, on-board mass emissions monitoring systems, such as a system previously disclosed by the inventor, and (4) portable on-board mass emissions monitoring systems, such as the one disclosed in U.S. patent application Ser. No. 09/359,984, the aggregate disclosure of which is incorporated herein by reference.
Systems of the type in the first category lack the portability necessary to test a wide range of vehicles. Systems of the type in the second category are capable of only monitoring concentration of pollutants in the exhaust gas, and therefore lack the capability of accurately measuring and calculating mass emissions.
Systems of the type in the third category employ a five-gas analyzer drawing undiluted exhaust from the tailpipe and calculate mass exhaust flow from engine operating data obtained via a diagnostic link to the engine control unit. The system disclosed in U.S. patent application Ser. No. 09/359,984 describes two novel methods of exhaust mass flow monitoring. The first method uses an array of sensors temporarily mounted to a spark ignition engine to provide the necessary engine operating data. The second uses an inert gas injection system, where the exhaust flow is inferred from the dilution ratio from a small, known amount of inert gas injected into the exhaust system upstream from the sampling point.
However, even these two systems have certain limitations. First, the sensor array employed uses an inductive pickup to measure engine rpm on spark ignition engines, and is therefore not suitable for use with compression ignition engines such as diesel engines. While mass exhaust flow can still be measured in a diesel engine using the second approach, namely, with an inert gas injector, this approach is likely to require small modifications to the vehicle, such as drilling a hole into the exhaust system. Third, these systems are not capable of accurately measuring particulate material in emissions. This is in large part because the sampling methodology does not allow for the iso-kinetic sampling of particulate matter and for the dilution of the sample necessary for an accurate particulate matter emissions measurement.
Finally, it is known that emissions can be sampled using a proportional sampling system, which is a sampling system in which the sampling rate is proportional to the exhaust flow. However, this type of system requires the installation of a bulky proportional sampling system to the end of the tailpipe, and thus its use and portability is limited by the design of the vehicle and its exhaust system.
Hence, it would be useful to provide a portable, on-board mass emissions monitoring system which could be used on heavy-duty diesel engines and would allow for on-board measurement of mass gaseous as well as particulate matter emissions.
With parenthetical reference to the corresponding parts, portions or surfaces of the disclosed embodiment, merely for the purposes of illustration and not by way of limitation, the present invention provides an improved mass emissions measuring system (15) for an internal combustion engine (17), comprising a particulate monitor (16), at least one sensor (18, 22, 23 or 29) which may be temporarily attached to the engine for sensing operating parameters of the engine, and a processor (19) programmed to collect and manipulate data from the monitor and the sensor, whereby the particulate emissions of the engine may be calculated.
The system may further comprise a display (20) for displaying the particulate emissions of the engine, an exhaust sampling system (31) which is adapted to be temporarily connected between the exhaust system of the engine and the particulate monitor, and/or an opacity meter (56 or 58). The particulate monitor may comprise a first photometer (46), a second photometer (48), and an impactor (45) located upstream from the second photometer, whereby the impactor limits the size of particulates in the exhaust of the engine communicating with the second photometer. The system may further comprise a microbalance (59) adapted to measure the mass of the particulate matter in the exhaust communicating with the photometer. The sensor may be capable of sensing engine rpm, engine oil temperature, intake manifold pressure, or intake air temperature. The particulate monitor may be capable of measuring particulate mass, particulate surface area, particulate count, or the opacity of the emissions from the engine. The system may be adapted for use on-board a moving vehicle. The present invention also discloses a portable mass emissions measuring system for an internal combustion engine comprising a particulate monitor, an engine-control interface (21), and a processor programmed to collect and manipulate data from the monitor and the engine-control interface, whereby the particulate emissions of the engine may be calculated.
Accordingly, the general object of the present invention is to provide an improved mass emissions measuring system which is adapted to be used to determine real-world vehicle emissions.
Another object is to provide an improved emissions measuring system for determining particulate emissions of a vehicle.
Another object is to provide an improved emissions measuring system which is portable.
Another object is to provide an improved emissions measuring system which is designed for use on a wide variety of vehicles.
Another object is to provide an improved emissions measuring system which may be used on a vehicle without permanent modification to the vehicle.
Another object is to provide an improved emission measuring system which can be installed for use on a vehicle in a very short period of time.
Another object is to provide an improved emissions measuring system which may be used without displacing a vehicle from service.
Another object is to provide an improved emissions measuring system which allows for use with a large number of vehicles.
Another object is to provide an improved emissions measuring system which may be used to test large numbers of vehicles in a short period of time.
Another object is to provide an improved emissions measuring system which may be used on vehicles which do not have an engine electronic control unit.
Another object is to provide an improved emissions measuring system which has improved accuracy in measuring particulates.